I have been searching everywhere for some code and can't find anything that works. A very new newbie to php!!!

I need to have two drop down boxes on the index page of my website. The first drop down will have every country of the world in it and when the user selects their country the second drop down will populate with all the major cities from their country. I do not want this to be populated from the database but I want to be able to search my database with these selections in turn giving the user a list of peoples names, phone, email, suburb etc. from the database.

If anyone can help please do and it also needs to be easy to understand.